A natural energy generation apparatus that combines waves, gravity, and current does not exist, thus, an ocean current generation and a wave power generation will be used as a reference. As for other natural energy generation apparatuses, there are ones using solar heat, wind power, hydraulic power, and geothermal power.
1. An ocean current generation apparatus for converting the ocean water current into electric power by establishing a hydraulic turbine under the buoyant body that is placed on the surface of the ocean as shown, for example, in Japanese Patent Laid-open Publication No. 2004-68638.
2. A wave power generation apparatus that generates electric power by tying a rope to the floating body that is floating on the surface of the ocean, operating the compression pump by moving the spindle up and down through the pulley, thereby rotating the turbine generator as shown, for example, in Japanese Patent Laid-Open Publication No. 2004-211607.
Other than the above wave power generation apparatus, there is another wave power generation apparatus which produces an up and down airflow from the swell of the waves and applies it to the blade of the turbine for rotation.
However, the conventional technologies disclosed by the above noted patent documents 1 and 2 have the following problems.
The flow of the ocean water is mainly comprised of ocean current and tidal current, where the speed of the tidal current is said to be two times faster than that of the ocean current. However, even if electric power is generated by using a hydraulic turbine (propeller) with this tidal current of higher speed, the generated amount of electric power is small in comparison to the equipment fee, and further, since the current direction changes four times per day, the maintenance fee becomes costly. Moreover, by floating the floating body on the surface of the waves (swell) and connecting it to a rope for suspension, the amount of wave power generation produced by the potential energy, where the floating body moves up and down by the swell, is also small in comparison to the equipment fee and is not practical. Furthermore, although the turbine power generation from the airflow is practical in a small scale generation, in order to manufacture a large scale generation apparatus, the energy from the airflow alone is not sufficient, thus, it is extremely difficult to put this technology in a practical use from the cost versus effectiveness stand point.